Flotation method and apparatus



Dec. 12, 1961 H. u. ZIEMER FLOTATION METHOD AND APPARATUS 5 Sheets-Sheet 1 Filed Aug. 31, 1959 172 M27? zo r 19072.5 a 271277162" Dec. 12, 1961 H. u. ZIEMER FLOTATION METHOD AND APPARATUS 3 Sheets-Sheet 2 Filed Aug. 31. 1959 Dec. 12, 1961 H. u. ZIEMER 3,012,669

FLOTATION METHOD AND APPARATUS Filed Aug. 51, 1959 5 Sheets-Sheet 5 F1E.E

Jrzflzzzfor: 170215 [I Zz'ezzzer United States {Patent 3,012,669 FLOTATION METHOD AND APPARATUS Hans U. Ziemer, Lakeland, Fla, assignor to International Minerals & Chemical Corporation, a corporation of New York Filed Aug. 31, 1959, Ser. No. 837,260 2 Claims. (Cl. 209-464) The present invention generally relates to the art of beneficiating materials by flotation techniques, and more particularly to a novel method and apparatus for beneficiating ores and other substances by flotation.

The beneficiation of ores by froth-flotation techniques is of great importance to the ore beneficiation art. The flotation process is widely used fontreating metallic and non-metallic ores and, in addition, is receiving an ever widening application in other industries.

In many of the prior art flotation machines, the mineral feed, which is usually in the form of an aqueous pulp, is introduced horizontally into a flotation cell which is usually constructed substantially in the form of a cylinder or prism. The pulp is agitated and aerated in the flotation cell by a rapidly rotating impeller which rotates on a substantially vertical axis. The mineral-laden air bubbles separate from the other material and pass upwardly to the pulp level of the flotation cell to form a froth. The froth is then floated off of the top of the cell. Since the pulp is introduced laterally into such a flotation cell, in which the air bubbles are passing chiefly in an upward direction, it has been diflicult because of this difference in directions of flow to obtain a uniform distribution of air bubbles throughout the cross-section of the, cell. It has also been diflicult to float mineral particles of relatively large mass in such a flotation cell.

A different type of flotation cell has recently been developed which remedies some of the shortcomings of many of the prior art flotation machines. This new flotation cell is described in detail in copending United States patent. application Serial No. 754,765, filed August 13, 1958, now US. Patent No. 2,922,521 issued January 26, 1960. The apparatus described in the copending patent application includes an inlet conduit for containing a flowing stream of fluid, and a laterally diverging vertical conduit connected to the inflow conduit at the outflow end thereof for receiving the flowing stream of fluid from the inflow conduit. The laterally diverging conduit comprises a part of the flotation cell. A pump is connected in the inflow conduit line for pumping the flotation cell feed through the inflow conduit into the laterally diverging conduit. The present invention is directed to improvements in such flotation apparatus and to an improved method of operating such apparatus. When using such apparatus it has been possible, because of air and pump thrust upwardly into the diverging conduit, to effect a higher weight recovery of materials than can be obtained in more conventional flotation cells; for example, such cells as are used in Fagergren and Denver flotation machines.

It is, accordingly, an object of the present invention to provide a novel method of and apparatus for beneficiating ores. It is a further object of the invention to provide a method for controlling the discharge of tailing from flotation apparatus employing a diverging conduit flotation cell.

It is another object of the invention to provide a new flotation machine having a diverging conduit flotation cell.

These and further objects and advantages of the present invention will be apparent from the following description and accompanying drawings which illustrate one form of the invention.

In the drawings:

FIGURE 1 is a side elevational view, paitially broken, of two flotation units embodying certain of the features of the invention;

FIGURE 2 is a plan view of theapparatus illustrated in FIGURE 1; and

FIGURE 3 is a sectional view of one of the flotation units taken along the line 3-3 of FIGURE 2.

The present invention provides a method for controlling the discharge of tailing from flotation apparatus employing a diverging conduit flotation cell. The method may be readily understood from the following description and by referring to the drawings. Briefly, the method of the present invention comprises introducing an aqueous pulp upwardly into a laterally diverging conduit flotation cell, withdrawing a froth float from the flotation cell, withdrawing an aqueous pulp stream from a lower portion of the flotation cell, and regulating the rate of withdrawing the pulp stream so as to maintain a predetermined pulp density in the flotation cell.

In accordance with the method of the present invention, an aqueous slurryor pulp of an ore or other material is introduced upwardly into a laterally diverging conduit flotation cell. The ore is usually reagentized with flotation reagents prior to the flotation operation. The aqueous pulpis also usually aerated prior to introducing the pulp into the flotation cell; however, the aerating may take place in the flotation cell.

The aqueous slurry is preferably pumped upwardly into a bottom inlet of the flotation cell. Material overflowing the top of the cell flows into an adjacent funnel. The material that continues to float in the funnel is discharged by overflowing the funnel and the material that sinks in the funnel is recycled to the flotation cell.

In the apparatus and process described in the hereinbefore referred to application Serial No. 754,765, some of the non-floated, or underflow material from the funnel is removed as the tailing. The discharge of tailing in this manner is, however, difficult to control, especially when the feed to the flotation cell contains relatively coarse or large size particles. The flotation cell tends to either drain itself of the unfloated material or the unfloated material tends to accumulate in the flotation cell and sand up the whole cell, that is the unfloated material tends to build up in the cell to the point that the cell becomes inoperable. Also, in the apparatus and process described in application Serial No. 754,765, it is necessary to lift, by pump thrust, all of thetailings withdrawn from the funnel. is not necessary when follow-ing the teachings of this invention. Further the apparatus described in application Serial No. 754,765 is capable of operating efliciently at a pulp density which may be higher, in some cases as much as twice the solids content, than the pulp density normally used in conventional flotation machines. However, in order to efliciently maintain a high pulp density in the flotation cell, and to avoid by-passing of the material to be floated in the cell, it is necessary to adjustably control the rate of withdrawing the pulp stream from the lower portion of the flotation cell.

In accordance with the method of the present invention, the tailing is not removed from the funnel but is removed from a lower portion of the diverging conduit flotation cell. The rate of withdrawal of the tailing is controlled so as to maintain the pulp density in the lower portion of the cell at a substantially constant predetermined value. When, because of operational and/or feed fluctuations, the pulp density increases above the predetermined value, the-rate of withdrawal of the tailing is increased and conversely, when the pulp density decreases below the predetermined value, the rate of It will be apparent that this withdrawal is decreased. This method of control will be further described in the following description of the apparatus of this invention.

In general, the flotation apparatus of the invention comprises an inflow conduit for containing a flowing stream of fluid, a laterally diverging conduit connected to the inflow conduit adjacent the outflow end thereof for receiving the stream of fluid from the inflow conduit, an outflow conduit connected to a lower portion of said laterally diverging conduit, and a control valve in said outflow conduit operatively connected to said laterally diverging conduit. It is to be understood that the particular structure illustrated in the drawings is merely an illustrative embodiment of the general principles involved.

The apparatus provides a flotation cell having a bottom inlet and an overflow adjacent to the upper end of the flotation cell. Between the inlet and overflow, the flotation cell is defined by a rigid-walled laterally diverging conduit section. The flotation cells, in accordance with the present invention, illustrated in the drawings, are provided with an outflow conduit connected to a lower portion of the flotation cell through which non-floated material may be withdrawn from the cell. The outflow conduit is provided with a control valve which is operatively connected to the fluid in the flotation cell. The inflow conduit opens centrally or substantially centrally into the flotation cell from below and the pulp-air mixture emerges from the inlet pipe as a jet stream and rises in the flotation cell. The air-laden mineral particles continue to rise in the cell to the froth level.

Since the jet stream carries the solid entrained particles mainly vertically upwardly, in the same direction that the air bubbles are rising, the adherence of the solid particles to the air bubbles is greatly facilitated and at the same time a shaking or shearing of the solid particles from the bubbles is substantially reduced. For this reason the apparatus enables a reliable flotation of even unusually coarse particles with high etficiency.

A flotation apparatus embodying the principles of this invention is illustrated in the drawings. The apparatus illustrated in the drawings includes an inflow conduit 11 which is connected to the bottom of a rigid-walled, laterally diverging conduit or flotation cell 13. In FIGURES l and 2, two units are illustrated in series. The numerals are aflixed to the left hand unit shown in FIGURE 1 and corresponding parts in the right hand unit are designated by primes The following description refers to both flotation units, even though the prime symbols are not used, except where specifically noted or apparent from the drawings.

The flotation cell 13 is illustrated as an inverted pyramid having a rectangular horizontal cross section; however, the vertical diverging conduit may take on other forms such as an inverted cone. The cell 13 has a substantially vertical axis and the walls thereof diverge laterally with increasing elevation. The point angle of the cell is preferably from about 20 to about 50. The cell also preferably has a height from about 1.5 to about 3.5 times the width of the cell. The inflow conduit 11 is also a discharge conduit of a pump 15. The inflow conduit 11 extends vertically upwardly and is provided with an extension 17 (FIG. 3) into the flotation cell. In general, the length of the extension 17 into the flotation cell depends upon the feed rate and the ratio of floated material to non-floated material. For example, when beneflciating different materials at substantially the same inflow conditions, if the ratio changes from 1:2 to 1:4, the extension 17 is preferably of relatively longer length in the latter operation.

The flotation cell 13 is provided with an inclined bottom 19 spaced below the outlet opening of the extension 17. The flotation cell 13 also has connected adjacent its lowermost point an outflow conduit 21 through which material may be withdrawn from the flotation cell.

The flotation cell 13 is provided at the top with vertical walls 23, 25, 27, and 29 which together form an open froth box. The upper edge of the wall 29 is somewhat lower than the upper edge of the other walls and provides a froth discharge means from the cell 13. An overflow weir 31 is suitably fixed in wall 29 and extends above the upper edge of this wall. The weir 31 is preferably adjustable in height by means not shown. A guide plate 33 is connected to the top edge of the wall 29 and curves downwardly to a funnel 35. The funnel 35 is of rectangular cross section and the upper edge of the inside vertical wall 37 of the funnel is connected to the guide plate 33. The funnel 35 is provided with four vertical walls which form a froth box on the funnel. The inside wall 37 and outside wall 41 are parallel. The other two parallel walls are extensions of walls 23 and 27 of the flotation cell 13 and the same numerals, therefore, designate these walls.

The wall 41 is somewhat lower than the other walls and is provided at its top edge with a chute 39, which serves as a froth discharging means. The chute 39 receives the discharge froth from the froth box of the funnel and delivers it to a discharge trough 51. The wall 41 is preferably provided on the inside with a weir 43, which is also vertically adjustable. The top edge of the weir 43 is provided with a downwardly inclined plate 45, over which a rotatable paddle wheel 47 is positioned. When in operation, the paddle wheel 47 rotates in the direction shown by A in FIGURE 3. A recycle conduit 49 connects the bottom of the funnel 35 to a fresh feed inlet conduit 53 which is connected to the suction end of the pump 15. A conduit 55 is also connected into the fresh feed inlet conduit 53. The conduit 55 has a throttle flap 57 therein. Air, usually under superatmospheric pressure, is introduced into inlet conduit 53 via conduit 55 to aerate the aqueous pulp.

A control valve 59 is positioned in the outflow conduit 21 through which the tailings are withdrawn from the flotation cell 13. As hereinbefore set forth, it has been determined that the operation of the flotation cell may be efliciently controlled by controlling the rate of tailing withdrawal through the outflow conduit 21. The control valve 59 adjustably controls this rate of withdrawal. The control valve 59 is operatively connected to the fluid in the flotation cell 13. The operation of the flotation cell 13 is preferably controlled by adjusting the rate of tailing withdrawal so as to maintain a substantially constant predetermined pulp density in the flotation cell and preferably in the lower portion of the flotation cell. The control valve 59 is, therefore preferably operatively connected to the fluid in the lower portion of the flotation cell 13 in a manner to maintain a substantially constant predetermined pulp density in the lower portion of the cell 13. The control valve is preferably rubber lined so as to reduce corrosion of the valve. In the illustrated embodiment the opening or closing of the control valve 59 is controlled by an automatic control device 61 which is diagrammatically illustrated in the drawing since such devices are well known and the specific construction of the device 61 forms no part of the invention. The control device 61 is operatively connected to the valve 59 by line 63. The control device 61 is also operatively connected to the interior of the lower portion of the flotation cell 13 by line 65. In the flotation unit shown in the right hand side of the drawing, the line 65 is connected to the outflow conduit 21' which in effect gives fluid communication with material in the lower portion of the cell. The device 61 receives a signal through line 65 which is proportional to the pulp density in the lower portion of the flotation cell and converts the signal into a form which adjusts the amount of opening of the control valve 59 thereby adjusting the rate of withdrawal of tailing through the outflow conduit 21. As hereinbefore stated, such control devices are well known in the art. The control valve 59 is controlled by the control device 61 in a manner density is at the predetermined density. Accordingly, as

the-pulp density increases, the opening of the valve 59 increases and the flow rate through conduit 21 increases. Similarly, the control valve 59 is controlled by the control device 61 in a manner such that when the pulp density in the lower portion of the flotation cell is below the predetermined density which it is desired to maintain, the valve is in a more relatively closed position and the rate of withdrawal of pulp through conduit 21 is less than when the pulp density is at the predetermined point. Accordingly, as the pulp density decreases, the opening of the valve 59 decreases and the flow rate through conduit 21 decreases.

In the embodiments illustrated in FIGURES l and 2, the material withdrawn through the conduit 21 and control valve 59 shown in the left hand side of the drawing continues through conduit 67 which corresponds to the fresh feed inlet conduit 53. The conduit 67' connects with the suction end of the pump and a flotation operation on the material introduced through conduit 67 is effected in the flotation unit illustrated in the right hand side of FIGURES 1 and 2 of the drawings. In this series flotation operation, two flotation units are illustrated as connected in series. Only one unit may, of course, be used and in a series operation two or more units may be used.

The method and apparatus of the present invention is eminently useful in the beneficiation of potash ores such as sylvinite, langbeinite, mixed ores, etc., phosphate ores, and the like. The method and apparatus operate efiiciently at large throughput. The method and apparatus also makes possible the beneficiation of larger size ore particles than are usually beneficiated in more conventional flotation machines.

The invention has been described with specific reference to certain process and construction details; however, it is to be understood that such details are illustrative only and not by way of limitation. Other modifications and equivalents will be apparent to those skilled in the art from the foregoing description.

Having now fully described and illustrated the invention, what is desired to be secured and claimed by Letters Patent is set forth in the appended claims.

What is claimed is:

1. A method of beneficiating an ore by froth flotation which comprises introducing an aqueous pulp of the ore upwardly along a flow path diverging laterally and uniformly in a vertical direction, withdrawing a froth float from the upper portion of the flow path, withdrawing substantially all tailings as an aqueous pulp stream from a lower portion of the flow path, sensing variations in the pulp density in the lower portion ofsaid flow path, and controlling the rate of withdrawing the pulp stream in accordance with the sensedpulp density variations to maintain a predetermined pulp density in the lower portion of the flow path in a manner such that when said pulp density increases above said predetermined pulp density, the rate of pulp withdrawal increases and when said pulp density decreases below said predetermined pulp density the rate of pulp withdrawal decreases.

2. A flotation apparatus which comprises a substantially vertical inflow conduit for containing a flowing stream of fluid and directing a generally vertical stream of fluid upwardly into a flotation cell, a laterally diverging vertical conduit flotation cell connected to said inflow conduit adjacent the upper outflow end thereof for receiving the generally vertical upwardly directed stream of fluid from said inflow conduit, means for withdrawing a froth float from an upper portion of said laterally diverging vertical conduit flotation cell while leaving the remaining fluid within said cell, an outflow conduit conduit connected to a lower portion of said laterally diverging conduit flotation cell for withdrawing fluid other than said froth fluid, and a control valve in said outflow conduit, sensing means operatively connected to the fluid in a lower portion of said laterally diverging conduit flotation cell for sensing variations in the density of fluid in said lower portion, said control being connected to said sensing means to regulate the rate of flow in said outflow conduit in response to variations in the density of the fluid in said lower portion of said laterally diverging conduit flotation cell.

References Cited in the file of this patent UNITED STATES PATENTS 2,142,207 Price Jan. 3, 1939 2,246,559 Weinig Q June 24, 1941 2,686,592 Miller Aug. 17, 1954 2,922,521 Schranz Jan. 26,1960 2,931,502 Schoeld Apr. 5, 1960 

1. A METHOD OF BENEFICIATING AN ORE BY FROTH FLOTATION WHICH COMPRISES INTRODUCING AN AQUEOUS PULP OF THE ORE UPWARDLY ALONG A FLOW PATH DIVERGING LATERALLY AND UNIFORMLY IN A VERTICAL DIRECTION, WITHDRAWING A FORTH FLOAT FROM THE UPPER PORTION OF THE FLOW PATH, WITHDRAWING SUBSTANTIALLY ALL TAILINGS AS AN AQUEOUS PULP STEAM FROM A LOWER PORTION OF THE FLOW PATH, SENSING VARIATIONS IN THE PULP DENSITY IN THE LOWER PORTION OF SAID FLOW PATH, AND CONTROLLING THE RATE OF WITHDRAWING THE PULP STREAM IN ACCORDANCE WITH THE SENSED PULP DENSITY VARIATIONS TO MAINTAIN A PREDETERMINED PULP DENSITY IN THE LOWER PORTION OF THE FLOW PATH IN A MANNER SUCH THAT WHEN SAID PULP DENSITY INCREASES ABOVE SAID PREDETERMINED PULP DENSITY, THE RATE OF PULP WITHDRAWAL INCREASES AND WHEN SAID PULP DENSITY DECREASES BELOW SAID PREDETERMINED PULP DENSITY THE RATE OF PULP WITHDRAWAL DECREASES. 